Field of the Invention
The present invention relates to a technical field of a lighting device, and more specifically, to a structure of a lighting device which enables an entire thickness to get thinner and can secure light efficiency.
Description of the Related Arts
An LED (Light Emitted Diode) device is a device which converts an electrical signal to infrared rays or light using a composition semiconductor property. Unlike a fluorescent lamp, since the LED device does not use harmful substances such as mercury and the like, it has a low possibility to cause environmental pollution and a long life span compared to a conventional light source. Also, it is advantageous that the LED device spends low electricity compared to the conventional light source and has excellent visibility and low brilliantness due to a high color temperature.
Accordingly, a current lighting device has been developed from a structure, in which a traditional light source such as a conventional incandescent lamp or a fluorescent lamp is used, to a structure, in which the aforesaid LED device is used as a light source. In particular, by using a light guide plate as disclosed in Korean Laid-Open Patent Publication No. 10-2012-0009209, the lighting device which performs a surface light-emitting function has been provided.
FIG. 1 and FIG. 2 schematically illustrate a conventional lighting device 1 which performs a surface light-emitting function. Referring to FIG. 1 and FIG. 2, the conventional lighting device 1 is configured such that a flat light guide plate 30 is disposed on a substrate 20, and a plurality of side view type LEDs 10 (only one LED being illustrated in the drawings) are disposed on a side of the light guide plate 30 in an array shape.
Light (L) incident to the light guide plate 30 from the LEDs 10 is reflected to an upper part by a minute reflection pattern or a reflection sheet 40 which is provided onto a bottom surface of the light guide plate 30 and is emitted from the light guide plate 30. Then, the light is emitted to the upper part of the light guide plate 30 and thus is provided to the outside through an external housing 50 made of a transparent material. Like the conceptual view as illustrated in FIG. 2, the lighting device 1 may be configured such that a plurality of optical sheets such as a diffusion sheet 31, prism sheets 32, 33, a protective sheet 34 and the like are further added between the light guide plate 30 and the external housing 50.
The aforesaid lighting device 1 functions to uniformly supply light to the outside. The light guide plate 30 is a component which functions to improve brightness of the light device 1 and to uniformly supply light. Also it is a kind of plastic mold lens to uniformly transmit the light emitted from a light source (LED). Accordingly, the light guide plate 30 is elementally used as an essential component of the conventional lighting device 1, but, due to a thickness of the light guide plate 30 itself, there is a limitation to make the thickness of an entire product thinner. As a material of the light guide plate 30 is not flexible, it is disadvantageous that it would be difficult to apply the light guide plate to the external housing 50, and thus a product plan and design cannot be easily changed.
Also, as the light is emitted from the side of the light guide plate to the outside, light loss is generated, thereby reducing light efficiency and brightness of the lighting device.
Moreover, because the LED which is a point light source is used, even though it is changed to a surface light source, there is a limitation to embody various lighting designs.